Marine reptiles like mosasaurs and plesiosaurs were clumsy on land. Big ones, like mosasaurus or liopleurodon would die pretty quickly out of water - their tremendous weight would literally crush them to death.

Flying reptiles like Pteranodon or quetzalcoatlus might work, as it’s been proven that they may have been a bit awkward on land, but could sort of “gallop”.

In all, it would be neat to see marine environment arenas or aerial arenas in-game, but something like that would take a while before it was released. We’re just going to have to wait and see.